Guided by the use of innovative nanoengineering, a team of researchers at the College of Nanoscale Science and Engineering at the University at Albany-SUNY is making vital contributions in the increasingly important area of homeland security.
A team led by Fatemeh (Shadi) Shahedipour-Sandvik, an assistant professor of nanoengineering at CNSE, working in collaboration with scientists at GE Global Research, has developed a compact UV laser source that holds promise for use in bio-agent detection systems. The research was funded by the U.S.Department of Homeland Security.The wideband gap III nitrides are of particular interest because they have numerous applications in electronic and optoelectronic devices.While the success rate in improving blue laser diode and blue-green LEDs has been remarkable over the past decade, there are still many challenges to be overcome for successful applications as UV emitters and lasers.
AlGaN alloy is particularly important in such development, primarily because its alloy composition is adjustable, with a wide band gap ranging from 3.4 eV (GaN) to 6.2eV (AlN). At the same time, difficulties in cleaving and dry etching of III nitrides without causing substantial damage is a problem facing development of high-efficiency mirrors for nitride lasers.
As a result of this research, the team is in the process of developing a novel technique in the fabrication of high Al composition AlGaN lasers, where the laser cavity is grown, as opposed to being fabricated. Hexagonal pyramids and trapezoidal features obtained by this technique are not only better in crystalline quality, but also possess a strong opticalconfinement. Thus, the geometry of each pyramid forms a high finesse cavity due to the total internal reflection by facets. These smooth facets are stabilized by the difference in the growth rates of (0001) and (1-101) facets.
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